1. Field of the Invention
The invention generally relates to a driving apparatus and a driving method, and more particularly, to a driving apparatus of a backlight module and a driving method thereof.
2. Description of Related Art
The multimedia technology has been quickly evolving due to the development of semiconductor devices or display devices. As to displays, liquid crystal display (LCD) has gradually become the mainstream in the display market thanks to its many advantages such as high image quality, high space efficiency, low power consumption, and no radiation. Because a LCD panel itself does not emit light, a backlight module has to be disposed below the LCD panel to provide a surface light source, so as to allow the LCD panel to display images.
Generally speaking, backlight modules may be categorized into side-type backlight modules and direct-type backlight modules. Besides, they may also be categorized into cold cathode fluorescent lamp (CCFL) backlight modules and light emitting diode (LED) backlight modules based on the types of light sources thereof In a direct-type backlight module, because the light directly enters the user's eyes, a longer light mixing distance is required for evenly mixing the light, which causes the thickness of the backlight module to be increased. Instead, in a side-type backlight module, the light is evenly mixed by a light guide plate before it enters the user's eyes, so that the side-type backlight module is relatively thinner.
In recent years, the size of LCD has been increased constantly. A direct-type backlight module can divide an entire LCD panel into a plurality of light-emitting regions, and the luminance corresponding to each light-emitting region is regulated according to the image content within the light-emitting region (i.e., a local dimming technique), so as to enhance the contrast ratio of the frame. However, when a dynamic frame is displayed, the foreground object moves quickly. In this case, flicker may be produced on the moving object (i.e., the moving object may blink) if the luminance of the light-emitting regions is regulated through a local dimming technique.
FIG. 1 is a diagram illustrating how a liquid crystal display (LCD) displays a dynamic frame by using a conventional local dimming technique. Referring to FIG. 1, herein it is assumed that the foreground object 110 has a higher grayscale value and the background has a lower grayscale value (i.e., the object 110 is brighter than the background). In a frame Fn, the object 110 almost takes up the entire display areas D1 and D2, and the corresponding light-emitting regions B1 and B2 provide higher luminance so that the object 110 is displayed as a brighter object.
In a frame Fn+1, the object 110 moves rightwards (i.e., the object 110′). Herein the object 110′ takes up the entire display area D2 but only about half of the display areas D1 and D3. Thus, the corresponding light-emitting region B2 provides a higher luminance while the light-emitting regions B1 and B3 provide a luminance about half of that provided by the light-emitting region B2. Because the light source is diffusible and the light-emitting regions B1 and B3 provide a lower luminance, the luminance of the light-emitting region B2 is distributed to the display areas D1 and D3 and accordingly the brightness of the object 110′ is reduced.
In a frame Fn+2, the object 110′ moves further rightwards (i.e., the object 110″). Herein the object 110″ takes up the entire display areas D2 and D3. Thus, the corresponding light-emitting regions B2 and B3 provide a higher luminance so that the object 110″ is again displayed as a brighter object. Accordingly, a bright, dark, and bright display effect is observed from the object 110 to the object 110″. Thereby, a flickering sensation is caused by the conventional local dimming technique when a foreground object moves quickly.